The present invention relates in general to a control circuit for a load such as an incandescent light, and pertains, more particularly, to a very low power drain control circuit preferably adapted as a direct replacement for a conventional wall switch and which automatically turns off a previously turned-on light or other load after a presetable period of time.
Different control schemes presently exist for controlling the lights in a room. For example, some of these systems employ detectors for determining the presence of an individual in a room and will, subsequently, turn the lights on and off once the person has left the room. Usually, these forms of control are quite complex and require a special separate control box. Furthermore, substantial additional wiring is usually necessary to provide this type of control.
Other available timer systems are mechanical in nature, costly, and have non-adjustable time periods or very short "on" time periods. Also, the available timer systems do not provide any means for alterting the user such as the flashing indication described herein. This flashing indication, in accordance with the invention alerts the user that the lights are about to go out.
One of the objects of the present invention is to provide an automatic light control that is of relatively simple construction and may be readily substituted directly for the normal switch assembly. The control of this invention may be readily replaced even by an unskilled person including a homeowner in much the same way that a dimmer is easily installed where a switch used to be located.
Another object of the present invention is to provide an automatic light control circuit that can be used for automatic control even in instances were only two active wires couple to the switch.
Still another object of the present invention is to provide a light or load control circuit automatically turning lights off after a predetermined period of time, and wherein the control requires only negligible power consumption, particularly in the "off" state.
In accordance with the above objects, the present invention provides an automatic form of control that may be embodied in a relatively small unit that can be used as a direct replacement for the conventional on-off switch that is normally mounted as a wall switch, perhaps to control the lights in a room, although, the control circuit of this invention may be used for controlling other loads. In accordance with the invention, the control is totally provided in a single unit that is substituted directly for the conventional on-off switch. The control circuit is adapted for use even with a two-wire connection at the switch. Thus, not requiring a third wire or ground at the unit. This third wire is usually a power lead.